Formation of Pillar-Ions in the Li Layer Decreasing the Li/Ni Disorder and Improving the Structural Stability of Cation-Doped Ni-Rich LiNi0.8Co0.1Mn0.1O2: A First-Principles Verification

A higher Ni content with less cobalt usage of lithium nickel cobalt manganese oxide cathode materials (LiNi x Co0.1Mn0.1O2, 0.6 ⟨ x ⟩ 0.9) provides a higher power rating and higher energy density in lithium-ion batteries (LIBs). However, severe Li/Ni mixing is one of the main reasons for poor cycling stability in these materials. Cation doping effectively suppresses the mixing of Ni ions in the lithium layer of LiNi x Co0.1Mn0.1O2. In this work, we investigate the effects of different cationic dopants (D) such as zirconium (Zr4+), zinc (Zn2+), calcium (Ca2+), magnesium (Mg2+), and aluminum (Al3+) in the Li layer, which act as a pillar for preventing degradation in the LiNi0.8–y Co0.1Mn0.1D y O2 (y = 0.033) cathode material for LIBs using density functional theory. In particular, a substituted dopant at the Ni3+-ion site suppresses the Ni3+-ion migration to the Li layer. During Li de-intercalation, the dopant migrates to the Li layer and acts as a pillar that enhances the structural stability. The pillared systems of both pristine and doped structures exhibit a more improved performance than non-pillared systems. An Al3+-doped pillared system displays a reduction in the height of the Li slab layer, resulting in a high Li diffusion energy barrier, which hinders easy Li diffusivity. However, the pillared systems doped with Zr4+- and Ca2+- in LiNi0.8–y Co0.1Mn0.1D y O2 act as better pillar-ions due to their high suppression energy of “neighbor Ni3+-ion migration”, facile Li-ion diffusion, and enhanced electrochemical structural stability.